As electronic apparatuses have had multi-functions, the apparatuses employ light-transmissible touch panels mounted on screens of displays, such as liquid crystal displays, of the apparatuses. A touch panel is simply manipulated by a user to allow him/her to view and select a character, an icon, and a symbol displayed on the screen with a finger or a dedicated pen for activating desired functions.
A conventional touch panel disclosed in Japanese Patent Laid-Open Publication No. 7-169367 will be explained. FIG. 5 is a cross sectional view of the conventional touch panel. A light transmissible upper resistor layer 3 made of, for example, indium tin oxide is provided on the lower surface of an upper substrate 1 made of light transmissible film. Similarly, a light transmissible lower resistor layer 4 made of, for example, indium tin oxide is provided on the upper surface of a lower substrate 2 made of light transmissible film. Plural dot spacers 5 made of insulating resin are provided at equal intervals on the upper surface of the lower resistor layer 4. A pair of upper electrodes (not shown) are provided on both ends of the upper resistor layer 3 while a pair of lower electrodes (not shown) are provided on both ends of the lower resistor layer 4 and extend in a direction orthogonal to the upper electrodes. The upper substrate 1 is bonded at its outer edge to the upper end of a frame-shaped spacer 6 by an adhesive layer (not shown) provided on the uppermost surface of the spacer 6. The lower substrate 2 has an outer rim bonded to the lower end of the spacer 6 by an adhesive layer (not shown) provided on the lower surface of the spacer 6. This arrangement allows the upper resistor layer 3 to face the lower resistor layer 4 at a predetermined space 7 between the layers.
The touch panel is mounted to a screen of a display, such as a liquid crystal display, and the upper and lower electrodes are connected to a control circuit (not shown) in an electronic apparatus.
A user presses the upper substrate 1 with a finger or a touch pen while viewing the screen of the display through the touch panel. The upper substrate 1 accordingly deflects and causes a pressed portion of the upper resistor layer 3 to contact the lower resistor layer 4. The control circuit supplies voltages to the upper and lower electrodes and measures a voltage ratio between the electrodes so as to determine the position of the pressed portion. The control circuit activates various functions of the electronic apparatus circuit according to the detected position.
The conventional touch panel is however constructed with a number of components, such as the upper substrate 1, the upper resistor layer 3, the space 7, the lower resistor layer 4, and the lower substrate 2. These components reflect external light at upper and lower surfaces of the components, thus reducing transparency. This disturbs the user's view of the display through the touch panel.
The space 7 may generate an optical interference pattern, such as a Newton's ring. The Newton's ring may be reduced by filling the space 7 with silicone oil or the like, however, this process increases the overall number of processes for manufacturing the touch panel, and thus makes the touch panel expensive.